2023-11-21 08:24:39
at Silvia Turin
An association has been identified between visceral fat and beta-amyloid accumulation in middle-aged people without disease. Abdominal fat promotes brain inflammation, one of the mechanisms underlying dementia
Higher amounts of visceral abdominal fat in middle age are linked to a greater risk of developing Alzheimer’s according to a research just presented at the annual meeting of the Radiological Society of North America (RSNA).
Obesity is Alzheimer’s
It has been known for some years that obesity is a significant factor in Alzheimer’s disease: a fact reported in various research. Excess weight can cause neuronal changes such as the accumulation of the beta-amyloid protein or the formation of brain damage generally associated with Alzheimer’s disease.
Which fat is bad for you?
RSNA researchers, however, for the first time have linked a specific type of fat (visceral fat) to the accumulation of the beta-amyloid protein in cognitively normal people.
Visceral fat is the fat that surrounds the internal organs and is located deep in the belly (therefore called visceral) and is not located at a subcutaneous level. According to research, it increases the risk of Alzheimer’s because it is related to changes that occur in the brain up to 15 years before the first symptoms of memory loss of the disease appear.
The experiment
To demonstrate this, the researchers analyzed the data of 54 cognitively healthy subjects, aged between 40 and 60, with an average Body Mass Index (BMI) of 32 (which determines first degree obesity). Participants underwent glucose and insulin measurements, as well as glucose tolerance tests. The volume of subcutaneous fat and visceral fat were measured using abdominal MRI. The brain MRI instead measured the cortical thickness of the brain regions that are usually affected by Alzheimer’s disease. Finally, PET (positron emission tomography) was used to examine the brain for the presence of amyloid plaques and tau tangles, proteins that are believed to interfere in communication between brain cells and are detected in large quantities in the brains of people suffering from Alzheimer’s.
The more visceral fat, the more amyloid
The scientists discovered that a higher proportion of visceral fat (compared to subcutaneous fat) was associated, in the subjects examined, with a greater concentration of amyloid (highlighted by PET) in an area of the cerebral cortex known to be the site of of amyloid accumulation in Alzheimer’s disease. This relationship was worse in men than in women, as men physiologically tend to accumulate belly fat, while women do so after menopause.
The researchers also found that higher measurements of visceral fat correlated with an increased burden of inflammation in the brain.
Simplifying, given the same body mass index, and therefore the degree of obesity, the state of the brain (with regards to the accumulation of proteins which can determine future risk of Alzheimer’s) was worse in people with a greater share of visceral fat compared to subcutaneous fat.
The mechanism
By going beyond body mass index and better characterizing the anatomical distribution of body fat on MRI, we now have a better understanding of why this factor may increase the risk of Alzheimer’s disease, said the study’s senior author, Dr. Cyrus A. Raji, Associate Professor of Radiology and Neurology and Director of Neuromagnetic Resonance at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis. “Several factors are assumed to play a role,” said MIR researcher Dr. Mahsa Dolatshahi: “The inflammatory secretions of visceral fat, as opposed to the potentially protective effects of subcutaneous fat, can lead to inflammation in the brain, one of the main mechanisms that contribute to Alzheimer’s disease.
The two types of fat
The subcutaneous fat, in fact, which women tend to accumulate on the hips and thighs, has a protective effect against heart attacks and strokes and an anti-inflammatory effect on the brain. For this reason, until menopause, women suffer less than men from a series of pathologies.
Visceral fat located on the abdomen, however, is dangerous: it lines the internal organs (such as the liver, heart and blood vessels), can produce pro-inflammatory and pro-tumor substances and increases the risk of cardiovascular diseases, sexual dysfunction, kidney problems and some tumors.
The belly is dangerous even in thin subjects
For this reason, the advice is to return to your ideal weight as soon as possible if you are overweight, but not only: a belly is dangerous even in thin people. A previous study published in JAMA found that menopausal women with normal weight but excess abdominal fat had a 31% greater risk of all-cause death. The risk was almost the same as in the obese group. This is why it is important to eliminate bacon for everyone: it is not just a blemish, it is the source of numerous health problems.
The optimal abdominal circumference for women is less than 80cm, abdominal obesity occurs with more than 88cm; for men they are 94cm and 102 (How to lose your belly after 50? See the article below, ed.).
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November 21, 2023 (changed November 21, 2023 | 07:20)
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